Nonlinear Least-Squares Frequency Offset Estimator and Its Simplified Versions for Flat-Fading Channels

In this paper, the nonlinear least-squares (NLS) estimator for frequency offset in flat-fading channels is systematically derived. A simple interpolation technique is introduced to improve the estimation accuracy of the resulting NLS estimator, especially when the number of zeros padded in FFT is insufficient. Furthermore, we propose an approximated NLS estimator which significantly simplifies the implementation complexity of the full structure NLS estimator. All the estimators derived in this paper do not require any information about the channel correlation as needed for most of the existing techniques. The simulation results show that the performances of two simplified NLS estimators are as good as that obtained from the full structure NLS estimator